1. Field of the Invention
The present invention relates to a method for obtaining a better color rendering with a photoluminescence plate, and more particularly to a technique for performing good color rendering of white light, above 90% color rendering and well mixed light by irradiating the photoluminescence plate having three colors with ultraviolet (UV) ray.
2. Description of Related Art
Researches and reports point out that the power consumption on lighting will be saved half through using the solid-state illuminant because the solid state illuminant can convert electricity to light more effectively than the incandescent lamp and the fluorescent lamp. Light emitting diode (LED) is a kind of solid-state illuminant and has a history of more than 30 years, however it is used on the pilots of the small-scale of electronic equipments till now. How can we accomplish more energy saving and create more advantages on environment through using the high-efficient solid-state illuminant more widely? Many developing countries are still using the lighting systems based on fuel. Maybe they can jump over the lighting system with electrical-net and enter into the LED lighting era of white light with solar energy directly. Moreover, there are questions on cost, polluting, and lighting quality resulted from burning the kerosene or other fuel for lighting. It is really worth studying on using the solid-state illuminant because the solid-state illuminant can reduce the global lighting cost and decrease the release of the greenhouse gases.
In the conventional technique, the light emitting mechanism on the white LED is divided into two ways basically. One is the mainstream way on commercialization is based on Nichia's technique at present, that is coating a layer of yttrium-aluminum-garnet fluorescent material on the InGaN chip of a blue LED with 460 nm wavelength and irradiating the layer of yttrium-aluminum-garnet fluorescent material with the blue LED to produces a yellow light of 555 nm wavelength which is the complementary color of blue, and then the blue light and the yellow light are mixed to produce a macroscopic white light on the basis of the lens principle. However, the white light produced from such way lacks red in the spectrum and causes an object to perform yellowish-red as the red object was irradiated.
Another way of the light emitting mechanism on the white LED developed by Sumitomo Electric Industries is based on Zinc Selenide (ZnSe) material, but the luminescence efficiency is not good enough. Furthermore, Toyada Gosei cooperated with Toshiba to obtain the white light of good color rendering converted from the three kind of fluorescent materials irradiated with UV individually by using UV LED and three kinds of fluorescent materials through mixing three primary colors (R, G and B).
However, the encapsulation of the foregoing white LED is limited on the small-scale range of illumination device and results in the focus effect and worse light uniformity.
The conventional technique use a fluorescent material irradiated with a blue LED to produces a yellow light of 555 nm wavelength which is the complementary color of blue, then the blue light and the yellow light are mixed to produce a macroscopic white light on the basis of the lens principle. However; the white light produced from such way lacks red in the spectrum and causes an object to perform yellowish-red as the red object was irradiated.
In addition to, the white light has good color rendering converted from the three kind of fluorescent materials irradiated with UV individually by using UV LED and three kind of fluorescent materials through mixing three primary colors (R, G and B), but there is the problem on color unevenness.
Therefore, the present invention provides a method for obtaining better color rendering to obviate the disadvantages of the conventional techniques.